/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * fs/vfs/fs_select.c
 *
 *   Copyright (C) 2008-2009, 2012-2013 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <sys/select.h>
#include <sys/time.h>

#include <string.h>
#include <poll.h>
#include <errno.h>
#include <assert.h>
#include <debug.h>

#include <tinyara/kmalloc.h>
#include <tinyara/cancelpt.h>
#include <tinyara/fs/fs.h>

#include "inode/inode.h"

#ifndef CONFIG_DISABLE_POLL

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/
static int _set_timeout(FAR struct timeval *timeout)
{
	/* Any negative value of msec means no timeout */
	int msec = -1;
	if (timeout) {
		/* Calculate the timeout in milliseconds */
		msec = timeout->tv_sec * 1000 + timeout->tv_usec / 1000;
	}

	return msec;
}

static int _init_desc_list(int nfds,
						  FAR fd_set *readfds,
						  FAR fd_set *writefds,
						  FAR fd_set *exceptfds,
						  struct pollfd *pollset)
{
	int fd;
	int ndx;

	for (fd = 0, ndx = 0; fd < nfds; fd++) {
		int incr = 0;

		/* The readfs set holds the set of FDs that the caller can be assured
		 * of reading from without blocking.  Note that POLLHUP is included as
		 * a read-able condition.  POLLHUP will be reported at the end-of-file
		 * or when a connection is lost.  In either case, the read() can then
		 * be performed without blocking.
		 */
		if (readfds && FD_ISSET(fd, readfds)) {
			pollset[ndx].fd = fd;
			pollset[ndx].events |= POLLIN;
			incr = 1;
		}

		/* The writefds set holds the set of FDs that the caller can be assured
		 * of writing to without blocking.
		 */
		if (writefds && FD_ISSET(fd, writefds)) {
			pollset[ndx].fd = fd;
			pollset[ndx].events |= POLLOUT;
			incr = 1;
		}

		/* The exceptfds set holds the set of FDs that are watched for exceptions */
		if (exceptfds && FD_ISSET(fd, exceptfds)) {
			pollset[ndx].fd = fd;
			pollset[ndx].events |= POLLERR;
			incr = 1;
		}

		ndx += incr;
	}

	return ndx;
}

static void _reset_fds(FAR fd_set *readfds, FAR fd_set *writefds, FAR fd_set *exceptfds)
{
	if (readfds) {
		memset(readfds, 0, sizeof(fd_set));
	}
	if (writefds) {
		memset(writefds, 0, sizeof(fd_set));
	}
	if (exceptfds) {
		memset(exceptfds, 0, sizeof(fd_set));
	}
}

static int _back_desc_list(int npfds,
						  FAR fd_set *readfds,
						  FAR fd_set *writefds,
						  FAR fd_set *exceptfds,
						  struct pollfd *pollset)
{
	int ndx;
	int ret = 0;
	for (ndx = 0; ndx < npfds; ndx++) {
		/* Check for read conditions.  Note that POLLHUP is included as a
		 * read condition.  POLLHUP will be reported when no more data will
		 * be available (such as when a connection is lost).  In either
		 * case, the read() can then be performed without blocking.
		 */
		if (readfds) {
			if (pollset[ndx].revents & (POLLIN | POLLHUP)) {
				FD_SET(pollset[ndx].fd, readfds);
				ret++;
			}
		}

		/* Check for write conditions */
		if (writefds) {
			if (pollset[ndx].revents & POLLOUT) {
				FD_SET(pollset[ndx].fd, writefds);
				ret++;
			}
		}

		/* Check for exceptions */
		if (exceptfds) {
			if (pollset[ndx].revents & POLLERR) {
				FD_SET(pollset[ndx].fd, exceptfds);
				ret++;
			}
		}
	}

	return ret;
}

/****************************************************************************
 * Name: select
 *
 * Description:
 *   select() allows a program to monitor multiple file descriptors, waiting
 *   until one or more of the file descriptors become "ready" for some class
 *   of I/O operation (e.g., input possible).  A file descriptor is
 *   considered  ready if it is possible to perform the corresponding I/O
 *   operation (e.g., read(2)) without blocking.
 *
 *   NOTE: poll() is the fundamental API for performing such monitoring
 *   operation under NuttX.  select() is provided for compatibility and
 *   is simply a layer of added logic on top of poll().  As such, select()
 *   is more wasteful of resources and poll() is the recommended API to be
 *   used.
 *
 * Input parameters:
 *   nfds - the maximum fd number (+1) of any descriptor in any of the
 *     three sets.
 *   readfds - the set of descriptions to monitor for read-ready events
 *   writefds - the set of descriptions to monitor for write-ready events
 *   exceptfds - the set of descriptions to monitor for error events
 *   timeout - Return at this time if none of these events of interest
 *     occur.
 *
 *  Return:
 *   0: Timer expired
 *  >0: The number of bits set in the three sets of descriptors
 *  -1: An error occurred (errno will be set appropriately)
 *
 ****************************************************************************/

int select(int nfds, FAR fd_set *readfds, FAR fd_set *writefds, FAR fd_set *exceptfds, FAR struct timeval *timeout)
{
	struct pollfd *pollset = NULL;
	int errcode = OK;
	int npfds;
	int fd;
	int ret;

	/* select() is a cancellation point */
	(void)enter_cancellation_point();

	/* How many pollfd structures do we need to allocate? */

	/* Initialize the descriptor list for poll() */
	for (fd = 0, npfds = 0; fd < nfds; fd++) {
		/* Check if any monitor operation is requested on this fd */
		if ((readfds && FD_ISSET(fd, readfds)) || (writefds && FD_ISSET(fd, writefds)) || (exceptfds && FD_ISSET(fd, exceptfds))) {
			/* Yes.. increment the count of pollfds structures needed */
			npfds++;
		}
	}

	if (npfds > 0) {
		/* Allocate the descriptor list for poll() */
		pollset = (struct pollfd *)kmm_zalloc(npfds * sizeof(struct pollfd));
		if (!pollset) {
			set_errno(ENOMEM);
			leave_cancellation_point();
			return ERROR;
		}
	}

	/* Initialize the descriptor list for poll() */
	/* And set up the return values */
	int ndx = _init_desc_list(nfds, readfds, writefds, exceptfds, pollset);

	DEBUGASSERT(ndx == npfds);
	if (ndx != npfds) {
		set_errno(EBADF);
		return ERROR;
	}

	/* Then let poll do all of the real work. (timeout: unit of millisecond)*/
	ret = poll(pollset, npfds, _set_timeout(timeout));
	if (ret < 0) {
		/* poll() failed! Save the errno value */
		errcode = get_errno();
	}

	_reset_fds(readfds, writefds, exceptfds);

	/* Convert the poll descriptor list back into selects 3 bitsets */
	if (ret > 0) {
		ret = _back_desc_list(npfds, readfds, writefds, exceptfds, pollset);
	}

	if (pollset) {
		kmm_free(pollset);
	}

	/* Did poll() fail above? */
	if (ret < 0) {
		/* Yes.. restore the errno value */
		set_errno(errcode);
	}

	leave_cancellation_point();
	return ret;
}

#endif							/* CONFIG_DISABLE_POLL */
